With both sides entrenched along a continuous front, the predominating
problem was: How to break through the enemy's defences to the open
ground beyond the last trenches, and then force the final decision.
In 1915, the Allies had endeavoured unsuccessfully to solve it; in
1916, the Germans, in turn, had suffered their severest check before
Verdun.
Putting experience to profit, the Allies now sought to apply the
methods of piercing on broader lines.
The defences having increased in strength and depth, the blow would
require to be more powerful, precise, and concentrated as to space and
time.
After the attacks of September, 1915, the French Staff set down as an
axiom that "material cannot be combatted with men." Consequently, no
more attacks without thorough preparation; nothing was to be left to
chance.
The orders issued to the different arms, divisions, battalions,
batteries, air-squadrons, etc., were recorded in voluminous plans of
attack, the least of which numbered a hundred pages.
Thousands of aerial photographs were taken and assembled; countless
maps, plans and sketches made. Everything connected with the coming
drama was methodically arranged: the staging, distribution of the
parts, the various acts.
Such was the intellectual preparation which, lasting several months,
was carried out simultaneously with the equipping of the front line.